Thermoelectric material gets flexible, efficient
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Last time I looked into this, the holy grail seems to be flexible thermoelectric combined with a daylight radiative cooling coating.
TEDs work the better the higher the temp differential is. And big copper heatsinks probably won't work on a wrist. So you couple the other side of the TED to a flexible meta‑material tuned to radiate heat in the specific IR window the Earth's atmosphere is transparent to, effectively using outer space as your "cold sink".
One lab even made a working sample, though the practicality of that might be decades away. It's one thing to have a nano‑material that works in the lab, another altogether to have it work outside of it, especially on something as prone to abrasion as clothing...
TEDs work the better the higher the temp differential is. And big copper heatsinks probably won't work on a wrist. So you couple the other side of the TED to a flexible meta‑material tuned to radiate heat in the specific IR window the Earth's atmosphere is transparent to, effectively using outer space as your "cold sink".
One lab even made a working sample, though the practicality of that might be decades away. It's one thing to have a nano‑material that works in the lab, another altogether to have it work outside of it, especially on something as prone to abrasion as clothing...
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This technology is already in production, although it currently needs another energy source (in the case of the powerwatch, this is solar https://www.powerwatch.com/) to achieve enough production to actually run the device. It's good to hear it's advancing far enough to where it may be able to run an AppleWatch though! That would be game changing.
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Maybe this and that and "ultra-thin thermoelectric films could be applied directly onto the chips to provide cooling and harvest power at the same time" in aggregate would give a combined effect robust enough in different environments? There's often a lot of solar when the air is body temp hot.
I don't see any thermal or solar approach that could eliminate charging outright; a hot indoor space doesn't offer a lot of opportunity.
Some kind of generator based on movement, like an electronic version of mechanical self-winding watches, also could be a promising component.
All that said, charging my watch for an hour every day or two isn't that much of a hardship.
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"The team argues in their study that ultra-thin thermoelectric films could be applied directly onto the chips to provide cooling and harvest power at the same time. "
So power would be input to a film to cool a chip, and power would be harvested from the chip's heat, at the same time? Something is not right here.
Or do you have two films, the inner one cools and the outer one harvests power? In this case the power harvesting layer will slow the transfer of energy to the environment, making more work for the cooling layer.
Also, comparing "a power output of 1.2 milliwatts per square centimeter "
with "84.2 milliamps to produce that 11.7 Kelvin difference" is impossible without knowing the voltage., and the area being cooled.
So power would be input to a film to cool a chip, and power would be harvested from the chip's heat, at the same time? Something is not right here.
Or do you have two films, the inner one cools and the outer one harvests power? In this case the power harvesting layer will slow the transfer of energy to the environment, making more work for the cooling layer.
Also, comparing "a power output of 1.2 milliwatts per square centimeter "
with "84.2 milliamps to produce that 11.7 Kelvin difference" is impossible without knowing the voltage., and the area being cooled.
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Longer than that. I remember hearing about shit like that in the 80's. Some kind of clothing-integrated something, be it cooling, heating, electricity generation, etc. always seemed to be a headline somewhere.
Still nothing that huge after 40+ years of promises. Incremental improvements at best (mostly in the water/sweat-wicking department and in insulation tech) with the PSU idea still very much a work in progress. Lots of new fabrics, though. So at least someone is making some money from all of it.
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What’s neat about this specifically when thinking about the Apple Watch is that the sensors used during a workout are the most power-draining. But usefully, when you work out your body temperature goes up increasing the differential. So it naturally generates more power when you need more power. That’s a nice feature.
That said, it doesn’t need to produce all the power the watch will use. Just extending the amount of time needed between charges is still a win.
That said, it doesn’t need to produce all the power the watch will use. Just extending the amount of time needed between charges is still a win.
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I am looking forward to wearing a very nice hat as my radiator to outer space.
View: https://www.youtube.com/watch?v=py_weA1D_u4
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I had a t-shirt which could have been used to tell the temperature if I had only calibrated a color chart for it. Mission accomplished! Only one downside - it made rings around my boobs. As a ten-year-old boy that did me no favors.
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I like their idea for cooling though; instead of focusing on the temp differential driving current, they're also looking at current driving temp differential, allowing this to work as a heat sink itself.
And any energy you bleed off as electric current isn't going to need a further heatsink or spectrum conversion, decreasing the reliance on radiative cooling.
This does mean, though that it might get somewhat uncomfortable to wear a strap of this stuff on a cool day, as the side on your skin seeks to match the ambient temperature. And on hotter days, it would be less effective as a current generator.
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Oh the era of HyperColor T-Shirts. I was always somewhat incredulous when people actually wore them to school. The main thing they did was highlighted your armpits.
I did see someone with a HyperColor paint job on their car once, and that was kind of neat; you could tell how hot the engine was running.
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They should be grounded for that comment, at least until they conduct themselves appropriately.
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So, either this is total BS or some researcher doesn't know how to use the kelvin temperature scale. Troubling either way, if you ask me.
See below
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How well will it work once integrated into the thicker material of a watch band? A metal band might work fine, but you’d want to be careful that the metal isn’t essentially providing a short-circuit around the material.
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Honestly, this doesn’t make any sense. Why is it that you think you can’t talk about temperature differences in Kelvin?
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It's been one of those days...I was trying to use a converter to tell me what 11.7 K was in C or F and all I got was the seriously large negative numbers. I blame the converters for my confusion having read the Wiki article again. Apologies. smdh
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Inching closer and closer to being that which powers the Matrix, just a matter of time.
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Extracting energy from humans as batteries, coupled with a form of fusion… paraphrasing from The Matrix
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Please don't compare a perfectly real thing to the beyond stupid insult to the most basic logic that is used in the matrix. thank you.
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FWIW kelvin is the preferred unit, as opposed to Celsius, when performing many science/engineering calculations, particularly when looking at energy or fluids. Less intuitive from the "how hot or cold does this feel" perspective, but using kelvins can avoid zero-offset coefficients from cluttering up equations. It perhaps feels a little pretentious to see kelvins being used in a conversation, but there's little doubt it's the unit in which the researchers report and think about their work.
Getting pedantic for a sec: per SI/NIST standards, kelvin only gets capitalized when it is abbreviated to its symbol K or begins a sentence . This goes for all units that are named for people. 'Celsius' is the lone the exception that always gets capitalized.
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Keith Tanner
Ars Tribunus Militum
This reads more like a good incremental improvement in both manufacturability and efficiency, which is what a lot of real world engineering looks like. It's not all massive breakthroughs. At some point, it'll become viable, and it looks like they're getting close.
I don't think watch bands flex that much in day to day use, so they probably only see a flex cycle when they're being put on or taken off. 1000 cycles would be 500 days in that case. 2% drop in efficiency every 18 months or so isn't too bad.
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yes, movement based is what occurred to me too, years ago. i’m not an engineer tho (not at all) so have nothing but an idea. and ideas are cheap, which is why i never cling to mine. i just keep hoping the will come into being.
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Measured with an infrared thermometer in my 20C apartment, my wrist is 32C, so a 12C differential max in my (normal) conditions. I don‘t see how you could even achieve that temperature differential, let alone 20K as mentioned in the article, as low above the skin as a wristband, with any significant heat flow.
The Carnot efficiency drops exponentially from 20C differential (6,4%) to my 12C (<4%) and the Seebeck-Effect of the wristband will be a fraction of that. All in all its an interesting technology for sure - for other use cases, but the conditions for even the 1-2mw/cm2 mentioned seem very optimistic on so many levels. Have they tested it on skin?
Maybe kinetic Energy harvesting instead, for our watches?
PS: Processor Energy consumption rises significantly with increased temperature, so insulating it with that thermoelectric film (operating at abysmal efficiency because of low temperature differential) is surely a net energy negative. (Though I fantasized about that too at one point).
The Carnot efficiency drops exponentially from 20C differential (6,4%) to my 12C (<4%) and the Seebeck-Effect of the wristband will be a fraction of that. All in all its an interesting technology for sure - for other use cases, but the conditions for even the 1-2mw/cm2 mentioned seem very optimistic on so many levels. Have they tested it on skin?
Maybe kinetic Energy harvesting instead, for our watches?
PS: Processor Energy consumption rises significantly with increased temperature, so insulating it with that thermoelectric film (operating at abysmal efficiency because of low temperature differential) is surely a net energy negative. (Though I fantasized about that too at one point).
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A delta of 20 degrees is no prob; just need that 16 C cool day, and to get the heat from somewhere closer to the 37 C human core temperature. A pair of flexible heat pipes will do it; the first one goes from the junction to the radiator, and the second one... does not. (Advert tagline: "Need ergs for your tech? Blow it out your ass!")
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My, you have such a short fuse! Don’t you see the great potential in his humor? Myself, I couldn’t resist being induced into a laughter.
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Gee, I have a watch that winds itself using the swinging motion of my arm when walking.
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Watch bands flex as you move your arm and wrist, just nowhere near as much as when you take them off. Depending on how the material responds to small changes in shape, the small changes the band experiences while being worn could be a huge problem or not much of a problem.
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Think it depends on the watch. I have a G-Shock Rangeman and I charge it once a week (if that). It has exercise tracking, heart rate monitoring, all of the things I need from a digital watch.
YMMV
YMMV
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Wouldn't movement be easier? While they were mechanical, self-winding watches existed for decades. There's a lot of power in people's random movements: that seems a lot easier to tap that a small thermal difference (that won't work in warm climates).
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I have a Casio wrist watch. I don't know the model any more because the stainless back has worn smooth after about forty years on my wrist. It uses a 399-type button cell which I change every other year whether it needs it or not.Think it depends on the watch. I have a G-Shock Rangeman and I charge it once a week (if that). It has exercise tracking, heart rate monitoring, all of the things I need from a digital watch.
YMMV
It gains about 320ms per day at 20C with a temperature coefficient of roughly, er, 10ms/day/K.
If I want to check my pulse I press my fingers to my wrist and look at the watch.
I don't usually bother, even on a thirty mile bike ride...
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Bulova tried this back in the late 70's with their Thermatron watch, which sadly never really made it to full production..
Bulova Thermatron
Bulova Thermatron
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I just carry a sundial and a compass. Sure, it doesn’t give me email notifications, but I never have to charge it.
Aren’t we done with dumb-ass statements about the devices we use that don’t need as much power because they don’t actually do as much? We’ve been wading through this nonsense since the first articles about smart watches. How about we give it a rest, hm?
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